Hello,
I have a Dell-branded monitor, model D1728D-LS, that has an issue.
Yesterday, it was working fine until mid-afternoon when the viewing
area changed to an vertical 2"-wide rectagle. It did not crop the
image, rather the width of the monitor was compressed into this
rectangular area.

I've tried turning it off/on, disconnecting the cable (the "check
signal" message was squiggly and also appeared illegibly about 2 inches
wide), and I connected another monitor to the same machine...the other
monitor displayed the screen properly.

Is there any other troubleshooting to do (I have a basic/moderate
understanding of electronics) or anything else to check or attempt to
configure?

Thank you,
Dave